Applicant's assignee has for many years designed, manufactured and sold safety pool covers of the type in which a cover of a strong mesh fabric reinforced by attached webbing strips is held taut over the water surface of a swimming pool by compression springs coupling the strips to anchors embedded in the concrete or other deck surface surrounding the pool. These covers are normally suspended above the entire water surface and extend beyond the edge of the pool about 12 to 18 inches onto the surrounding apron or deck surface so that there are no openings providing access to the water through which children or debris can fall or become lodged. The covers are designed to support the weight of a person and, in actual incidents, have supported lawn tractors, cows and even a car, without structural failure. While the mesh construction permits rain to drain through the cover, in winter a snow load of very considerable weight may build up and the cover must provide protection under such conditions. See, for example, U.S. Pat. No. 2,958,872 to Meyer, assigned to the same assignee, which shows and describes this type of pool cover.
These pool covers continue to provide excellent service and safety for the majority of pool applications. However, a problem which has existed for a long period without any satisfactory solution is now becoming more significant.
Swimming pools in previous years were predominantly rectangular or incorporated only simple outlines, with the entire pool edge at the same elevation above the water surface. This permitted mesh safety covers to easily overlap the peripheral coping surface surrounding the pool. Not only were dangerous openings avoided, but wind-blown debris was prevented from contaminating the pool water. However, more recently architects and pool designers have increasingly incorporated more sophisticated design elements such as slides, rough surface waterfalls, multi-level copings, steps to raised level spas, vertical walls, overhanging diving rocks, etc. All of these design features can represent obstructions, typically including a structure extending vertically higher than the basic peripheral coping surface, which prevent a pool cover from being stretched across the pool edge to provide an overlap at the location of the obstruction. As a result, an effort has usually been made to fit the pool cover around the vertical obstruction. However, without a securely fastened overlap, the fit of the cover to the obstruction can leave a gap whose size is dependent on the accuracy in measuring the pool, original cover tailoring, accuracy of cover installation, displacements after cover installation, etc. For example, a heavy snow load temporarily pulling the cover away from pool edges can cause an enlarged opening or gap between the cover and an obstruction. At irregularly shaped obstructions a particularly dangerous condition can result.
A further demand for closer fitting covers has been introduced by the issuance of a Consumer Product Safety Commission sponsored, and ASTM drafted, Emergency Standard for Safety Swimming Pool Covers intended to reduce child drownings (American Society of Testing Materials standard ES-13). This Standard mandates the absence of any openings large enough to permit a small child's head from gaining access to the water, specifically providing for:
Perimeter Deflection Test-With a weight of 50 lbs. on the cover at a distance of at least 4 ft. (but not exceeding 6 ft.) the cover shall not deflect away from the pool enough to allow a perimeter test object (an ellipsoidal 3.7".times.5.7" and 36.6 lbs. weight object), to gain access to the water.
Openings Test-No opening shall exist between the edge of the cover and the deck surface and coping wall or both or the top surface of the spa or pool, large enough to permit a solid-faced spherical test object with a maximum breadth of 4.5" and a steadily applied force of 40.+-.1 lbs. to pass through to the water.
Previous attempts to solve this problem have not provided a satisfactory solution in general, and particularly with respect to reliably securing openings at irregularly-shaped obstructions and to maintaining secure closure under disruptive conditions such as heavy snow loading. Prior attempts have included waterbag pillows, extra flaps of pool cover material or plastic-flaps, which have generally been too difficult or costly to install, aesthetically unattractive and ineffective to a greater or lesser degree. For example, use of plastic flaps at obstructions is subject to the difficult requirements that the flap must simultaneously be rigid enough to securely close a gap, flexible enough to shape itself to the contour of the obstruction and must maintain both these contradictory characteristics at low temperature conditions so as to readily adapt to changing snow loads in the middle of the winter. It should be noted that while certain prior approaches may be suitable for application to specific forms of obstructions under static conditions, a satisfactory solution must provide secure closure of openings for a wide range of structural shapes and installations, under dynamic variations of loading, temperature and other environmental conditions.
It is, therefore, an object of this invention to provide a pool cover having a compressible safety edge for resiliently filling openings between pool cover edges and obstructions.
It is a further object to provide a swimming pool safety system in which spring assemblies couple the pool cover to poolside anchors so that the compressible safety edge is held in place at an obstruction to resiliently secure the opening during both static and changing load conditions.